In a semiconductor device such as an LED and a power module, a structure in which semiconductor element is bonded onto a circuit layer made of a conductive material is provided.
In a power semiconductor element for high-power control used for controlling wind power generation, an electric vehicle, a hybrid vehicle, and the like, a heating value is large. Therefore, as a substrate on which the power semiconductor element is mounted, for example, a power module substrate including a ceramic substrate made of AlN (aluminum nitride), Al2O3 (alumina), and the like, and a circuit layer which is formed by bonding a metal sheet excellent in conductivity to one face of the ceramic substrate have been widely used from the related art. As the power module substrate, a substrate in which a metal layer is formed by bonding a metal sheet to the other face of the ceramic substrate is also provided.
For example, in PTL 1, a power module substrate, in which an aluminum plate serving as a circuit layer is bonded to one face of the ceramic substrate made of AlN (aluminum nitride) via an Al—Si-based brazing material and an aluminum plate serving as a metal layer is bonded to the other face of the ceramic substrate via an Al—Si-based brazing material, has been proposed.
In such a power module substrate, a semiconductor element as a power element is mounted on the circuit layer via a solder layer to be used as a power module. In addition, a copper heat sink may be bonded to a metal layer side via solder.
In addition, in PTLs 2 to 5, a ceramic circuit board, in which a ceramic substrate and an aluminum plate are bonded to each other using a brazing material containing Mg, and Mg or the like is unevenly distributed in a bonded interface between the brazing material and the aluminum plate or a bonded interface between the brazing material and the ceramic substrate, has been proposed.
In these ceramic circuit boards, a bonding property between the ceramic substrate and the aluminum plate is improved by removing an oxide which inhibits bonding by unevenly distributed Mg.